This application claims the priority benefit of Taiwan application serial no. 90102494, filed Feb. 6, 2001.
1. Field of the Invention
The present invention relates to a method for fabricating a slide. More particularly, the present invention relates to a method for fabricating a transmission electron microscope slide..
2. Description of the Related Art
Cross sectional analysis is considered an effective technology in the failure analysis of very large semiconductor integrated (VLSI) devices. Scanning electron microscopes (SEM) are instruments used in cross sectional observation. However, where device density is very high, the resolution of scanning electron microscopes tends to be very poor. Thus, as fabrication processes gradually enter the VLSI stage, scanning electron microscopes have been gradually replaced by transmission electron microscopes (TEM). In order to resolve problems related to yield and device dependability; the use of TEM to perform failure analysis has become more and more prevalent.
In present-day, advanced copper fabrication processes, a barrier layer, used to prevent the diffusion of copper particles, is often formed in via holes, trench openings and damcene openings. Afterwards, the barrier layer is then covered with a copper-seed (Cu-seed) layer. The step-coverage quality of the barrier layer and Cu-seed layer affects the quality of the subsequently formed metal plug and the conductive line. Thus, it necessary to make use of cross-sectional analysis technology to determine whether or not the quality of the barrier layer and Cu-seed layer conform to given standard That is to say, cross-sectional analysis is used to determine whether the step-coverage quality and thickness of the barrier and Cu-seed layers are acceptable, in order to raise operational effectiveness and dependability, as well as to raise yield and lower fabrication costs.
The openings observed under a conventional transmission electron microscope are generally filled with platinum, tungsten nitride or an oxide material. These materials are used to provide a dependable support structure as well as to provide a greater contrast when viewed through the TEM microscope. The greater contrast makes it possible to determine clearly whether or not the barrier layer and Cu-seed layers have been formed well.
However, if platinum or tungsten is used as a filler material, the platinum and tungsten appear as a dark image when the quality and thickness of the barrier layer and Cu-seed layer are observed under the TEM. The lack of contrast between the Cu-seed layer and the barrier layer makes it extremely difficult to discern the two layers.
Moreover, when chemical vapor deposition is conducted in the opening to form a filler of oxide material or nitride material, the Cu-seed layer melts as a result of the high temperature which causes Cu-agglomeration. The melting of the Cu-seed layer can occur even when a low-temperature deposition process (300xc2x0 C.), such as plasma enhanced CVD, PECVD, is performed. It then becomes impossible to determine clearly the actual thickness of the Cu-seed layer from the image under the TEM, which would impair the inspection.
Accordingly, the present invention provides a fabrication method for a TEM slide. The method comprises providing a die. A thermal adhesive is deposited over a surface of several device structures formed on the die. The thermal adhesive is covered by a glass piece. A polishing step is conducted to a non-device side of the die to form a thin sheet from the die. The glass piece is then removed, to expose the thermal adhesive. A layer comprising sacrificial material is then formed above the exposed thermal adhesive on the thin sheet. An ion transmission step is then conducted to form a TEM slide from the thin sheet.
As embodied and broadly described herein, a TEM slide fabrication method is provided, according to a preferred embodiment of the present invention, wherein the glass transition temperature of the thermal adhesive is approximately 90xc2x0-100xc2x0 C. and the approximate temperature of the thermal adhesive covering the die is about 90xc2x0-100xc2x0 C.
The glass transition temperature of the thermal adhesive is approximately between 90xc2x0-100xc2x0 C. This temperature is lower, in relation to the temperature of plasma enhanced CVD and the melting point of metal. The low-temperature thermal adhesive used to fill openings prevents the thermal adhesive from damaging the crystal seed layer. In the case where the seed layer is a Cu-seed layer, Cu-agglomeration can be avoided.
Additionally, the thermal adhesive when viewed under the TEM electron microscope provides excellent contrast. Thus, the profile of the stacked layer can be clearly distinguished, which increases the accuracy of inspection results.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.